Question

Find the value of x.​

Answer 1

-7

Explanation:

∠D = ∠B

2x² + 7 = x² - 8x

2x² - x² + 8x + 7 = 0

x² + 8x + 7 = 0

(x + 7)(x + 1) = 0

x = -7 or -1

For x = -7, we have

x² - 8x = 49 + 56 = 105

2x² + 7 = 2*49 + 7 = 105 Right, x = -7 is an answer

For x = -1, we have

x² - 8x = 1 + 8 = 9 < 90

In the diagram angle B is > 90, so x = -1 is not the answer.